Protective effects of the fructooligosaccharide on the growth performance, hematology, immunology indicators and survival of tambaqui (Colossoma macropomum, Characiformes: Serrasalmidae) infected by Aeromonas hydrophila

Prebiotics are nutraceuticals that can be effective in therapeutic treatments by stimulating the immune system of fish. So, they contribute to reducing the use of antibiotics and synthetic drugs which are harmful to aquatic biota, fish health and human. The main goal of this study was to evaluate the potential effect of fructooligosaccharide (FOS) on zootechnical performance, blood immunology, phagocytic activity of white blood cells and survival of juveniles of Colossoma macropomum infected by Aeromonas hydrophila. The trials were composed of five diet levels of FOS (0; 0.1; 0.5; 1.0 and 2.0%), in triplicates. The experiments extended over 63 days, 45 days for the zoothecnical performance experiment and plus 18 days for the A. hydrophila challenge. An improvement in growth rate, mainly final body mass (BFW), weight gain (WG), feed efficiency (FE) and specific growth rate in animals fed 0.1% and 0.5% FOS supplemented diet was observed. An increase in circulating white blood cells (WBC), among them, a special granulocytic cell (PAS-GL(+)) in animals fed FOS was also observed. The percentage of phagocytosis was higher in animals fed 0.5; 1 and 2% FOS. Consequently, after experimental infection, a higher survival of animals feeding diets containing FOS was observed, in particular those feeding 0.5% FOS supplemented diet. These results show that the addition of FOS in diets for C. macropomum at concentrations of 0.1 and 0.5% has important beneficial effects. Therefore, it is concluded that FOS can be used to promote growth and improve the healthiness of tambaqui, an important commercial Amazonian fish raised worldwide.